Apparatus to communicatively couple three-wire field devices to controllers in a process control system

ABSTRACT

Example apparatus to communicatively couple three-wire field devices to controllers in a process control system are disclosed. An example terminal block is disclosed that includes a first interface including termination points to couple with a field device, a second interface to couple with a shared bus of a termination panel, wherein the shared bus is to remain coupled to a controller when the terminal block is removed, a third interface to couple with a power bus of the termination panel, and a fuse disposed between the first interface and the third interface.

RELATED APPLICATION

This patent arises from a continuation of U.S. patent application Ser.No. 14/609,801, which was filed on Jan. 30, 2015. U.S. patentapplication Ser. No. 14/609,801 is hereby incorporated herein byreference in its entirety. Priority to U.S. patent application Ser. No.14/609,801 is hereby claimed.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to process control systems and,more particularly, to apparatus to communicatively couple three-wirefield devices to controllers in a process control system.

BACKGROUND

Process control systems, like those used in chemical, petroleum,pharmaceutical, pulp and paper, or other manufacturing processes,typically include one or more process controllers communicativelycoupled to at least one host including at least one operator workstationand to one or more field devices configured to communicate via analog,digital or combined analog/digital communication protocols. The fielddevices, which may be, for example, device controllers, valves, valveactuators, valve positioners, switches and transmitters (e.g.,temperature, pressure, flow rate, and chemical composition sensors) orcombinations thereof, perform functions within the process controlsystem such as opening or closing valves and measuring or inferringprocess parameters. A process controller receives signals indicative ofprocess measurements made by the field devices and/or other informationpertaining to the field devices, uses this information to implement acontrol routine, and generates control signals that are sent over thebuses or other communication lines to the field devices to control theoperation of the process control system.

A process control system can include a plurality of field devices thatprovide several different functional capabilities and that are oftencommunicatively coupled to process controllers using two-wire interfacesin a point-to-point (e.g., one field device communicatively coupled to afield device bus) or a multi-drop (e.g., a plurality of field devicescommunicatively coupled to a field device bus) wiring connectionarrangements or with wireless communications. Some field devices areconfigured to operate using relatively simple commands and/orcommunications (e.g., an ON command and an OFF command). Other fielddevices are more complex requiring more commands and/or morecommunication information, which may or may not include simple commands.For example, more complex field devices may communicate analog valueswith digital communications superimposed on the analog value using, forexample, a Highway Addressable Remote Transducer (“HART”) communicationprotocol. Other field devices can use entirely digital communications(e.g., a FOUNDATION Fieldbus communication protocol).

Some field devices (e.g., photoelectric or capacitive sensors) areimplemented using a three-wire architecture to enable communications aswell as to provide power to such devices. Typically, such three-wirefield devices are coupled to an external power source (and associatedexternal fuse) to power the device in addition to being coupled to oneor more I/O cards.

SUMMARY

Example apparatus to communicatively couple three-wire field devices tocontrollers in a process control system are disclosed. An exampleterminal block is disclosed that includes a first interface includingtermination points to couple with a field device, a second interface tocouple with a shared bus of a termination panel, wherein the shared busis to remain coupled to a controller when the terminal block is removed,a third interface to couple with a power bus of the termination panel,and a fuse disposed between the first interface and the third interface.

An example termination panel is disclosed that includes a shared bus, apower bus, a plurality of terminal blocks to couple with a controllervia the shared bus, at least a first one of the terminal blocksincluding a first interface including termination points to couple witha field device, a second interface to couple with the shared bus,wherein the shared bus is to remain coupled with the controller when thefirst one of the terminal blocks is removed, a third interface to couplewith the power bus, and a fuse disposed between the first interface andthe third interface.

An example process control system is disclosed that includes acontroller, a termination panel including a shared bus and a power bus,the termination panel including a plurality of terminal blocks coupledto the termination panel to couple with the controller via the sharedbus, at least a first one of the terminal blocks including a firstinterface including termination points to couple with a field device, asecond interface to couple with the shared bus, wherein the shared busis to remain coupled with the controller when the first one of theterminal blocks is removed, a third interface to couple with the powerbus, and a fuse disposed between the first interface and the thirdinterface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating an example process controlsystem.

FIG. 2 is a detailed diagram of the example marshalling cabinet of FIG.1.

FIGS. 3A-3C depict top, side, and end views, respectively, of theexample terminal block constructed in accordance with the teachingsdisclosed herein.

FIG. 4 is a side view of the example terminal block of FIGS. 3A-3C withthe example termination module of FIGS. 1 and 2 partially insertedtherein.

FIG. 5 is a schematic diagram of an example wiring of a 3-wire fielddevice to the example terminal block of FIGS. 3 and 4 installed withinthe example marshalling cabinet of FIGS. 1 and 2.

FIG. 6 is a schematic diagram of a wiring of the 3-wire field device ofFIG. 5 to a known terminal block installed within the examplemarshalling cabinet of FIGS. 1 and 2.

FIG. 7 is a schematic diagram of an example wiring of a 2-wire fielddevice to the example terminal block of FIGS. 3 and 4 installed withinthe example marshalling cabinet of FIGS. 1 and 2.

DETAILED DESCRIPTION

Although the following describes example apparatus and systemsincluding, among other components, software and/or firmware executed onhardware, it should be noted that such systems are merely illustrativeand should not be considered as limiting. For example, it iscontemplated that any or all of these hardware, software, and firmwarecomponents could be embodied exclusively in hardware, exclusively insoftware, or in any combination of hardware and software. Accordingly,while the following describes example apparatus and systems, persons ofordinary skill in the art will readily appreciate that the examplesprovided are not the only way to implement such apparatus and systems.

An example process control system includes a control room (e.g., acontrol room 108 of FIG. 1), a process controller area (e.g. a processcontroller area 110 of FIG. 1), a termination area (e.g., a terminationarea 140 of FIG. 1), and one or more process areas (e.g., process areas114 and 118 of FIG. 1). A process area includes a plurality of fielddevices that perform operations (e.g., controlling valves, controllingmotors, controlling boilers, monitoring, measuring parameters, etc.)associated with performing a particular process (e.g., a chemicalprocess, a petroleum process, a pharmaceutical process, a pulp and paperprocess, etc.). Some process areas are not accessible by humans due toharsh environment conditions (e.g., relatively high temperatures,airborne toxins, unsafe radiation levels, etc.). The control roomtypically includes one or more workstations within an environment thatis safely accessible by humans. The workstations include userapplications that users (e.g., engineers, operators, etc.) can access tocontrol operations of the process control system by, for example,changing variable values, process control functions, etc. The processcontrol area includes one or more controllers communicatively coupled tothe workstation(s) in the control room. The controllers automate controlof the field devices in the process area by executing process controlstrategies implemented via the workstation. An example process strategyinvolves measuring a pressure using a pressure sensor field device andautomatically sending a command to a valve positioner to open or close aflow valve based on the pressure measurement. The termination areaincludes a marshalling cabinet that enables the controllers tocommunicate with the field devices in the process area. In particular,the marshalling cabinet includes a plurality of termination modules usedto marshal, organize, or route signals from the field devices to one ormore I/O cards communicatively coupled to the controllers. The I/O cardstranslate information received from the field devices to a formatcompatible with the controllers and translate information from thecontrollers to a format compatible with the field devices.

Known techniques used to communicatively couple field devices within aprocess control system to controllers involve using a separate bus(e.g., a wire, a cable, or a circuit) between each field device and arespective I/O card communicatively coupled to a controller (e.g., aprocess controller, a programmable logic controller, etc.). An I/O cardenables communicatively coupling a controller to a plurality of fielddevices associated with different data types or signal types (e.g.,analog in (AI) data types, analog out (AO) data types, discrete in (DI)data types, discrete out (DO) data types, digital in data types, anddigital out data types)) and different field device communicationprotocols by translating or converting information communicated betweenthe controller and the field devices. For example, an I/O card may beprovided with one or more field device interfaces configured to exchangeinformation with a field device using the field device communicationprotocol associated with that field device. Different field deviceinterfaces communicate via different channel types (e.g., analog in (AI)channel types, analog out (AO) channel types, discrete in (DI) channeltypes, discrete out (DO) channel types, digital in channel types, anddigital out channel types)). In addition, the I/O card can convertinformation (e.g., voltage levels) received from the field device intoinformation (e.g., pressure measurement values) that the controller canuse to perform operations associated with controlling the field device.The known techniques require a bundle of wires or buses (e.g., amulti-core cable) to communicatively couple a plurality of field devicesto I/O cards.

Unlike these known techniques that use a separate bus to communicativelycouple each field device to corresponding I/O cards, some knownapparatus and methods communicatively couple field devices to an I/Ocard by terminating a plurality of field devices at a termination panel(e.g., a marshalling cabinet) and using one bus (e.g., a conductivecommunication medium, an optical communication medium, a wirelesscommunication medium) communicatively coupled between the terminationpanel and the I/O card to communicatively couple the field devices tothe I/O card. Such apparatus and methods are disclosed in U.S. Pat. No.8,332,567, filed on Sep. 19, 2006; U.S. Pat. No. 8,762,618, filed onDec. 10, 2012; U.S. Pat. No. 9,495,313, filed on Jan. 31, 2014; and U.S.Pat. No. 9,411,769, filed on Jan. 8, 2015; all of which are herebyincorporated by reference in their entireties. In brief, such techniquesinvolve using an example universal I/O bus (e.g., a common or sharedcommunication bus) that communicatively couples a plurality oftermination modules to one or more I/O cards communicatively coupled toa controller. Each termination module is communicatively coupled to oneor more respective field devices using a respective field device bus(e.g., an analog bus or a digital bus) from each field device thatterminates on a terminal block that is communicatively coupled with acorresponding termination module. In some examples, the terminationmodules are CHARMs (characterization modules) developed by EmersonProcess Management. The termination modules are configured to receivefield device information from the field devices via the field devicebuses and communicate the field device information to the I/O cards viathe universal I/O bus by, for example, packetizing the field deviceinformation and communicating the packetized information to the I/Ocards via the universal I/O bus. The I/O card(s) can extract the fielddevice information received via the universal I/O bus and communicatethe field device information to the controller, which can thencommunicate some or all of the information to one or more workstationterminals for subsequent analysis. Likewise, the I/O cards can packetizethe field device information from workstation terminals and communicatethe packetized field device information to the plurality of terminationmodules via the universal I/O bus. Each of the termination modules canthen extract or depacketize respective field device information from thepacketized communications received from a respective I/O card andcommunicate the field device information to a respective field device.

Each of the termination modules may be coupled to a different type offield device that communicates using a different communication protocol.As such, in addition to relaying information between the I/O cards andthe field devices, the termination modules communicate with thecorresponding field devices using a first communication protocolassociated with the field device and communication with the I/O cardsbased on a second protocol associated with the universal I/O bus. Thus,while different termination modules may use different communicationprotocols to communicate with particular field devices, all of thetermination modules use the same communication protocol to communicatewith the I/O cards. In this manner, the communications back to thecontroller are significantly simplified.

Communications with many field devices in a process control system areimplemented using a two-wire architecture. For example, in a 2-wirediscrete input (DI) field device, one wire is used to feed (e.g., powerand/or apply an electrical signal to) a contact input of the fielddevice and cause current to flow when the contact is closed. The secondwire in a 2-wire DI field device is used for the output signal of thefield device that serves as the input to the process control system(e.g., provides feedback indicating whether the contact is open orclosed). Known terminal blocks provide interfaces to directly coupleeach of the two-wires to a controller in a process control system and/ora termination module as described above which, in turn, communicateswith a controller.

By contrast, some field devices are 3-wire field devices that have threewires to enable communications and provide power to the field device tooperate. For example, in a 3-wire DI field device, a first wire is usedto feed (e.g., power and/or apply an electrical signal to) the fielddevice and the contact input. A second wire of a 3-wire DI field deviceis used specifically to power the field device. A third wire is used forthe output signal of the field device that serves as the input to theprocess control system. While there are known terminal blocks that canbe communicatively coupled directly with a 2-wire field device, thereare no terminal blocks that can be communicatively coupled with a 3-wireDI field device without additional components and complexity. Forexample, a 3-wire field device may be wired to a known terminationmodule for purposes of communications via a known terminal (2-wire)block but the field device must also be wired to an external powersource to power the device. Such wiring can involve as many as fiveexternal wire terminals in addition to the two used to connect wires tothe terminal block. That is, there are two wire terminals associatedwith the terminal block, an additional two terminals associated with theexternal power source, and three more terminals to enable the couplingof each of the three wires of the field device with the terminal blockand the external power source. Furthermore, adding an external powersource in this manner also requires the use of an external fuse betweenthe external power source and the 3-wire field device to protect againsta short circuit as the power source is not typically energy limited.These additional components and wiring requirements result in increasedcost and complexity to implement a 3-wire field device. Some knownsystems employ specially manufactured terminal blocks to facilitate thewiring of such 3-wire field devices. However, when an engineer or otherplant personnel desires to change the signal sensing components attachedto such a terminal block (e.g., the DI electronics), the terminal blockand all the associated wiring needs to be undone and/or removed.Furthermore, known terminal blocks for 3-wire DI field devices do notinclude a fuse such that additional components are still required.

The example terminal blocks constructed in accordance with the teachingsdisclosed herein overcome the above complexities to facilitate thedirect coupling of 3-wire field devices to a process control system. Insome examples, the terminal blocks disclosed herein include three wireterminals on which each of the three wires of a 3-wire DI field devicemay be landed to directly couple the field devices to the correspondingtermination modules. In some examples, the terminal blocks arecommunicatively coupled to an external power source to provide power toeach of the termination modules to provide the necessary power to thecorresponding 3-wire field devices. That is, in some examples, the needto separately couple each 3-wire field device to an external powersource is avoided because the terminal blocks provide an interfacebetween the power source and the field devices. Further, in someexamples, a fuse is built into the terminal blocks disclosed herein toprovide surge protection without the need for a separate external fuse.In some such examples, the fuse is replaceable. In some examples, theterminal blocks disclosed herein enable the replacement or changing oftermination modules containing the signal sensing components (e.g., theDI electronics contained within the corresponding termination modules)without removing the terminal blocks and/or without unwiring thecorresponding field devices to the terminal blocks. As a result, theinitial wiring, maintenance, and/or updating of wiring for 3-wire DIfield devices is substantially simplified with fewer components to saveboth time and money and reduce an overall footprint of the system.

Now turning to FIG. 1, an example process control system 100 is shownimplemented according to the teachings of U.S. Pat. No. 8,332,567. Theexample process control system of 100 includes a workstation 102communicatively coupled to a controller 104 via a bus or local areanetwork (LAN) 106, which is commonly referred to as an applicationcontrol network (ACN). The LAN 106 may be implemented using any desiredcommunication medium and protocol. For example, the LAN 106 may be basedon a hardwired or wireless Ethernet communication protocol. However, anyother suitable wired or wireless communication medium and protocol couldbe used. The workstation 102 may be configured to perform operationsassociated with one or more information technology applications,user-interactive applications, and/or communication applications. Forexample, the workstation 102 may be configured to perform operationsassociated with process control-related applications and communicationapplications that enable the workstation 102 and the controller 104 tocommunicate with other devices or systems using any desiredcommunication media (e.g., wireless, hardwired, etc.) and protocols(e.g., HTTP, SOAP, etc.). The controller 104 may be configured toperform one or more process control routines or functions that have beengenerated by a system engineer or other system operator using, forexample, the workstation 102 or any other workstation and which havebeen downloaded to and instantiated in the controller 104. In theillustrated example, the workstation 102 is located in a control room108 and the controller 104 is located in a process controller area 110separate from the control room 108.

In the illustrated example, the example process control system 100includes field devices 112 a-c in a first process area 114 and fielddevices 116 a-c in a second process control area 118. To communicateinformation between the controller 104 and the field devices 112 a-c and116 a-c, the example process control system 100 is provided with fieldjunction boxes (FJB's) 120 a-b and a termination panel or marshallingcabinet 122. Each of the field junction boxes 120 a-b routes signalsfrom respective ones of the field devices 112 a-c and 116 a-c to themarshalling cabinet 122. The marshalling cabinet 122, in turn, marshals(e.g., organizes, groups, etc.) information received from field devices112 a-c and 116 a-c and routes the field device information torespective I/O cards (e.g., I/O cards 132 a-b and 134 a-b) of thecontroller 104. In the illustrated example, the communications betweenthe controller 104 and the field devices 112 a-c and 116 a-c arebidirectional so that the marshalling cabinet 122 is also used to routeinformation received from I/O cards of the controller 104 to respectiveones of the field devices 112 a-c and 116 a-c via the field junctionboxes 120 a-b.

In the illustrated example, the field devices 112 a-c arecommunicatively coupled to the field junction box 120 a and the fielddevices 116 a-c are communicatively coupled to the field junction box120 b via electrically conductive, wireless, and/or opticalcommunication media. For example, the field junction boxes 120 a-b maybe provided with one or more electrical, wireless, and/or optical datatransceivers to communicate with electrical, wireless, and/or opticaltransceivers of the field devices 112 a-c and 116 a-c. In theillustrated example, the field junction box 120 b is communicativelycoupled wirelessly to the field device 116 c. In an alternative exampleimplementation, the marshalling cabinet 122 may be omitted and signalsfrom the field devices 112 a-c and 116 a-c can be routed from the fieldjunction boxes 120 a-b directly to the I/O cards of the controller 104.In yet another example implementation, the field junction boxes 120 a-bmay be omitted and the field devices 112 a-c and 116 a-c can be directlyconnected to the marshalling cabinet 122.

The field devices 112 a-c and 116 a-c may be Fieldbus compliant valves,actuators, sensors, etc., in which case the field devices 112 a-c and116 a-c communicate via a digital data bus using the well-known Fieldbuscommunication protocol. Of course, other types of field devices andcommunication protocols could be used instead. For example, the fielddevices 112 a-c and 116 a-c could instead be Profibus, HART, or AS-icompliant devices that communicate via the data bus using the well-knownProfibus and HART communication protocols. In some exampleimplementations, the field devices 112 a-c and 116 a-c can communicateinformation using analog communications or discrete communicationsinstead of digital communications. In addition, the communicationprotocols can be used to communicate information associated withdifferent data types. In some examples, one or more of the field devices112 a-c and 116 a-c are 2-wire field devices. In some examples, one ormore of the field devices 112 a-c and 116 a-c are 3-wire field devices.

Each of the field devices 112 a-c and 116 a-c is configured to storefield device identification information. The field device identificationinformation may be a physical device tag (PDT) value, a device tag name,an electronic serial number, etc. that uniquely identifies each of thefield devices 112 a-c and 116 a-c. In the illustrated example of FIG. 1,the field devices 112 a-c store field device identification informationin the form of physical device tag values PDT0-PDT2 and the fielddevices 116 a-c store field device identification information in theform of physical device tag values PDT3-PDT5. The field deviceidentification information may be stored or programmed in the fielddevices 112 a-c and 116 a-c by a field device manufacturer and/or by anoperator or engineer involved in installation of the field devices 112a-c and 116 a-c.

To route information associated with the field devices 112 a-c and 116a-c in the marshalling cabinet 122, the marshalling cabinet 122 isprovided with a plurality of termination modules 124 a-c and 126 a-ccommunicatively coupled to corresponding terminal blocks (e.g., theterminal blocks 206 a of FIG. 2) on the marshalling cabinet 122. Theterminal blocks provide a first physical interface (e.g., wiretermination points) onto which wires from the field devices 112 a-c and116 a-c may be landed, a second physical interface (e.g., a slot withelectrical contacts) to hold and communicatively couple the terminationmodules 124 a-c and 126 a-c, and a third physical interface tocommunicatively couple the terminal blocks to the marshalling cabinet122 and the controller 104. In this manner, communications between thecontroller 104, the termination modules 124 a-c and 126 a-c, and thefield devices 112 a-c and 116 a-c are enabled. The termination modules124 a-c are configured to marshal information associated with the fielddevices 112 a-c in the first process area 114 and the terminationmodules 126 a-c are configured to marshal information associated withthe field devices 116 a-c in the second process area 118. As shown, thetermination modules 124 a-c and 126 a-c are communicatively coupled tothe field junction boxes 120 a-b via respective multi-conductor cables128 a and 128 b (e.g., a multi-bus cable). In an alternative exampleimplementation in which the marshalling cabinet 122 is omitted, thetermination modules 124 a-c and 126 a-c and corresponding terminalblocks can be installed in respective ones of the field junction boxes120 a-b.

The illustrated example of FIG. 1 depicts a point-to-point configurationin which each conductor (including one or more wires) in themulti-conductor cables 128 a-b communicates information uniquelyassociated with a respective one of the field devices 112 a-c and 116a-c. For example, the multi-conductor cable 128 a includes a firstconductor 130 a, a second conductor 130 b, and a third conductor 130 c.Specifically, the first conductor 130 a is used to form a first data busconfigured to communicate information between the termination module 124a and the field device 112 a, the second conductor 130 b is used to forma second data bus configured to communicate information between thetermination module 124 b and the field device 112 b, and the thirdconductor 130 c is used to form a third data bus configured tocommunicate information between the termination module 124 c and thefield device 112 c. In an alternative example implementation using amulti-drop wiring configuration, each of the termination modules 124 a-cand 126 a-c can be communicatively coupled with one or more fielddevices. For example, in a multi-drop configuration, the terminationmodule 124 a can be communicatively coupled to the field device 112 aand to another field device (not shown) via the first conductor 130 a.In some example implementations, a termination module can be configuredto communicate wirelessly with a plurality of field devices using awireless mesh network. In some examples, where the field devices 112 a-care 3-wire field devices, the multi-conductor cable 128 a includesadditional conductors to transmit power to the field device 112 a-c.

Each of the termination modules 124 a-c and 126 a-c may be configured tocommunicate with a respective one of the field devices 112 a-c and 116a-c using a different data type. For example, the termination module 124a may include a digital field device interface to communicate with thefield device 112 a using digital data while the termination module 124 bmay include an analog field device interface to communicate with thefield device 112 b using analog data.

To control I/O communications between the controller 104 (and/or theworkstation 102) and the field devices 112 a-c and 116 a-c, thecontroller 104 is provided with the plurality of I/O cards 132 a-b and134 a-b. In the illustrated example, the I/O cards 132 a-b areconfigured to control I/O communications between the controller 104(and/or the workstation 102) and the field devices 112 a-c in the firstprocess area 114, and the I/O cards 134 a-b are configured to controlI/O communications between the controller 104 (and/or the workstation102) and the field devices 116 a-c in the second process area 118.

In the illustrated example of FIG. 1, the I/O cards 132 a-b and 134 a-breside in the controller 104. To communicate information from the fielddevices 112 a-c and 116 a-c to the workstation 102, the I/O cards 132a-b and 134 a-b communicate the information to the controller 104 andthe controller 104 communicates the information to the workstation 102.Similarly, to communicate information from the workstation 102 to thefield devices 112 a-c and 116 a-c, the workstation 102 communicates theinformation to the controller 104, the controller 104 then communicatesthe information to the I/O cards 132 a-b and 134 a-b, and the I/O cards132 a-b and 134 a-b communicate the information to the field devices 112a-c and 116 a-c via the termination modules 124 a-c and 126 a-c. In analternative example implementation, the I/O cards 132 a-b and 134 a-bcan be communicatively coupled to the LAN 106 internal to the controller104 so that the I/O cards 132 a-b and 134 a-b can communicate directlywith the workstation 102 and/or the controller 104.

To provide fault tolerant operations in the event that either of the I/Ocards 132 a and 134 a fails, the I/O cards 132 b and 134 b areconfigured as redundant I/O cards. That is, if the I/O card 132 a fails,the redundant I/O card 132 b assumes control and performs the sameoperations as the I/O card 132 a would otherwise perform. Similarly, theredundant I/O card 134 b assumes control when the I/O card 134 a fails.

To enable communications between the termination modules 124 a-c and theI/O cards 132 a-b and between the termination modules 126 a-c and theI/O cards 134 a-b, the termination modules 124 a-c are communicativelycoupled to the I/O cards 132 a-b via a first universal I/O bus 136 a andthe termination modules 126 a-c are communicatively coupled to the I/Ocards 134 a-b via a second universal I/O bus 136 b. Unlike themulti-conductor cables 128 a and 128 b, which use separate conductors orcommunication mediums for each one of the field devices 112 a-c and 116a-c, each of the universal I/O buses 136 a-b is configured tocommunicate information corresponding to a plurality of field devices(e.g., the field devices 112 a-c and 116 a-c) using the samecommunication medium. For example, the communication medium may be aserial bus, a two-wire communication medium (e.g., twisted-pair), anoptical fiber, a parallel bus, etc. via which information associatedwith two or more field devices can be communicated using, for example,packet-based communication techniques, multiplexed communicationtechniques, etc.

The universal I/O buses 136 a and 136 b are used to communicateinformation in substantially the same manner. In the illustratedexample, the I/O bus 136 a is configured to communicate informationbetween the I/O cards 132 a-b and the termination modules 124 a-c. TheI/O cards 132 a-b and the termination modules 124 a-c use an addressingscheme to enable the I/O cards 132 a-b to identify which informationcorresponds to which one of the termination modules 124 a-c and toenable each of the termination modules 124 a-c to determine whichinformation corresponds to which of the field devices 112 a-c. When atermination module (e.g., one of the termination modules 124 a-c and 126a-c) is connected to one of the I/O cards 132 a-b and 134 a-b, that I/Ocard automatically obtains an address of the termination module (from,for example, the termination module) to exchange information with thetermination module. In this manner, the termination modules 124 a-c and126 a-c can be communicatively coupled anywhere on the respective buses136 a-b without having to manually supply termination module addressesto the I/O cards 132 a-b and 134 a-b and without having to individuallywire each of the termination modules 124 a-c and 126 a-c to the I/Ocards 132 a-b and 134 a-b.

By providing the termination modules 124 a-c and the termination modules126 a-c that can be configured to use different data type interfaces(e.g., different channel types) to communicate with the field devices112 a-c and 116 a-c and that are configured to use respective common I/Obuses 136 a and 136 b to communicate with the I/O cards 132 a-b and 134a-b, the illustrated example of FIG. 1 enables routing data associatedwith different field device data types (e.g., the data types or channeltypes and corresponding communication protocols used by the fielddevices 112 a-c and 116 a-c) to the I/O cards 132 a-b and 134 a-bwithout having to implement a plurality of different field deviceinterface types on the I/O cards 132 a-b and 134 a-b. Therefore, an I/Ocard having one interface type (e.g., an I/O bus interface type forcommunicating via the I/O bus 136 a and/or the I/O bus 136 b) cancommunicate with a plurality of field devices having different fielddevice interface types.

In the illustrated example, the I/O card 132 a includes a data structure133 and the I/O card 134 a includes a data structure 135. The datastructure 133 stores the field device identification numbers (e.g.,field device identification information) corresponding to field devices(e.g., the field devices 112 a-c) that are assigned to communicate withthe I/O card 132 a via the universal I/O bus 136 a. The terminationmodules 124 a-c can use the field device identification numbers storedin the data structure 133 to determine whether a field device isincorrectly connected to one of the termination modules 124 a-c. Thedata structure 135 stores the field device identification numbers (e.g.,field device identification information) corresponding to field devices(e.g., the field devices 116 a-c) that are assigned to communicate withthe I/O card 134 a via the universal I/O bus 136 b. The data structures133 and 135 can be populated by engineers, operators, and/or users viathe workstation 102 during a configuration time or during operation ofthe example process control system 100. Although not shown, theredundant I/O card 132 b stores a data structure identical to the datastructure 133 and the redundant I/O card 134 b stores a data structureidentical to the data structure 135. Additionally or alternatively, thedata structures 133 and 135 can be stored in the workstation 102.

In the illustrated example, the marshalling cabinet 122 is shown locatedin a termination area 140 separate from the process control area 110. Byusing the I/O buses 136 a-b instead of substantially more communicationmedia (e.g., a plurality of communication buses, each uniquelyassociated with one of the field devices 112 a-c and 116 a-c or alimited group of them along a multi-drop segment) to communicativelycouple the termination modules 124 a-c and 126 a-c to the controller 104facilitates locating the controller 104 relatively farther from themarshalling cabinet 122 than in known configurations withoutsubstantially decreasing the reliability of communications. In someexample implementations, the process control area 110 and thetermination area 140 can be combined so that the marshalling cabinet 122and the controller 104 are located in the same area. In any case,placing the marshalling cabinet 122 and the controller 104 in areasseparate from the process areas 114 and 118 enables isolating the I/Ocards 132 a-b and 134 a-b, the termination modules 124 a-c and 126 a-cand the universal I/O buses 136 a-b from harsh environmental conditions(e.g., heat, humidity, electromagnetic noise, etc.) that may beassociated with the process areas 114 and 118. In this manner, the costand complexity of designing and manufacturing the termination modules124 a-c and 126 a-c and the I/O cards 132 a-b and 134 a-b can besubstantially reduced relative to the cost of manufacturingcommunications and control circuitry for the field devices 112 a-c and116 a-c because the termination modules 124 a-c and 126 a-c and the I/Ocards 132 a-b and 134 a-b do not require operating specificationfeatures (e.g., shielding, more robust circuitry, more complex errorchecking, etc.) required to guarantee reliable operation (e.g., reliabledata communications) as would otherwise be necessary to operate in theenvironmental conditions of the process areas 114 and 118.

Additional details and alternative example implementations that may beused to communicatively couple workstations, controllers, and I/O cards,as well as additional details and alternative example implementations ofthe example marshalling cabinet 122 and termination modules 124 a-c and126 a-c are disclosed in U.S. Pat. Nos. 8,332,567; 8,762,618; 9,495,313;and 9,411,769; all of which were incorporated above.

FIG. 2 is a detailed diagram of the example termination panel ormarshalling cabinet 122 of FIG. 1. In the illustrated example, themarshalling cabinet 122 includes a baseplate 202 that is provided with asocket rail 204. The socket rail 204 of the illustrated example isstructured to receive terminal blocks 206 a-c to which the terminationmodules 124 a-c may be communicatively coupled. In addition, themarshalling cabinet 122 is provided with an I/O bus transceiver 208 thatcommunicatively couples the termination modules 124 a-c to the universalI/O bus 136 a described above in connection with FIG. 1. The I/O bustransceiver 208 may be implemented using a transmitter amplifier and areceiver amplifier that conditions signals exchanged between thetermination modules 124 a-c and the I/O cards 132 a-b. The marshallingcabinet 122 is provided with another universal I/O bus 210communicatively coupling the terminal modules 124 a-c (via the terminalblocks 206 a-c) to the I/O bus transceiver 208. In some examples,multiple baseplates 202 may be communicatively coupled to enableadditional termination modules to be communicatively coupled to the I/Otransceiver 208. In some such examples, the baseplates are provided withconnectors 212 to interconnect the I/O bus 210 across each baseplate 202as successive baseplates 202 are attached to an underlying support frame214 (e.g., a DIN rail).

Using a common communication interface (e.g., the I/O bus 210 and theI/O bus 136 a) to exchange information between the I/O cards 132 a-b andthe termination modules 124 a-c enables defining field device-to-I/Ocard connection routing late in a design or installation process. Forexample, the termination modules 124 a-c can be communicatively coupledto the I/O bus 210 at various locations (e.g., various terminal blocks206 a-c in different sockets of the socket rail 204) within themarshalling cabinet 122. In addition, the common communication interface(e.g., the I/O bus 210 and the I/O bus 136 a) between the I/O cards 132a-b and the termination modules 124 a-c reduces the number ofcommunication media (e.g., the number of communication buses and/orwires) between the I/O cards 132 a-b and the termination modules 124a-c, thus enabling installation of relatively more of the terminationmodules 124 a-c (and/or the termination modules 126 a-c) in themarshalling cabinet 122 than the number of known termination modulesthat can be installed in known marshalling cabinet configurations.

To provide electrical power to the termination modules 124 a-c and theI/O bus transceiver 208, the marshalling cabinet 122 is provided with apower supply 218. In some examples, the termination modules 124 a-c usethe electrical power from the power supply 218 to power communicationchannels or communication interfaces used to communicate with fielddevices (e.g., the field devices 112 a-c of FIG. 1) and/or to providethe field devices electrical power for operation. Additionally oralternatively, in some examples as shown in the FIG. 2, each baseplate202 is provided with a local power bus 216 that may be connected to anexternal power source 220. The external power source 220 may be anysuitable power source such as 24 volts direct current (VDC) or 120/230volts alternating current (VAC). In some examples, the terminationmodules 124 a-c use the electrical power from the external power source220 to power communication channels or communication interfaces and/orto provide power to the field devices for operation. Providing powerthrough the local power bus 216 in this manner eliminates the need toseparately wire each 3-wire field devices requiring such power to anexternal power source. The cost of implementing the control system isreduced as a result of less time being needed to wire and maintain thesystem in addition to the costs saved from fewer components. In theillustrated example, although the termination modules 124 a-c may usepower from either the internal power supply 218 or the external powersource 220, in either case, communications with the I/O cards 132 a-bare still achieved via the I/O bus transceiver 208 over the I/O bus 210.Whether the termination modules 124 a-c use power from the internalpower supply 218 or the external power source 220 depends upon the typeor configuration of the terminal block used to interface the terminationmodules 124 a-c with the baseplate 202. That is, in some examples, theterminal block 206 a is provided with a plurality of connectors (e.g.,the baseplate connectors 310 of FIG. 3B) to electrically couple theterminal block 206 a to the baseplate 202. In some examples, at leastone of the connectors directly couples the termination module 124 a tothe local power bus 216 of the baseplate 202 (to provide power) while atleast one other connector directly couples the termination module 124 ato the universal I/O bus 210 of the baseplate 202 (to enablecommunications).

FIGS. 3A-3C depict a top view, a side view, and an end view,respectively, of the example terminal block 300, which may be similar oridentical to the terminal blocks 206 a-c of FIG. 2. FIG. 4 depicts aside view of the example terminal block 300 of FIGS. 3A-3C with theexample termination module 124 a of FIGS. 1 and 2 partially insertedinto a slot 301 of the terminal block 300. As shown in the illustratedexample of FIG. 4, the termination module 124 a is removably coupled tothe terminal block 300 via the slot 301. More particularly, the exampletermination module 124 a includes a plurality of contacts 302 thatcommunicatively couple and/or electrically couple the termination module124 a to corresponding contacts 304 of the terminal block 300 when thetermination module 124 a is inserted into the slot 301 of the terminalblock 300. In this manner, the termination module 124 a can beselectively removed and/or coupled to the termination block 300 whilethe termination block 300 is in place and coupled to the baseplate 202(FIG. 2) and/or communicatively coupled with a field device. In someexamples, the terminal block 300 includes a moveable latch 305 thateither releases the termination module 124 a or secures the terminationmodule 124 a in an installed position when the contacts 304 of terminalbock 300 are electrically coupled to the contacts 302 of the terminationmodule 124 a. Additionally or alternatively, in some examples, the latch305 selectively secures the termination module 124 a in a partiallyinstalled position. In the partially installed position, the terminationmodule 124 a is held in place within the slot 301 while preventingelectrical contact between contacts 302, 304 of the termination module124 a and the terminal block 300 (similar to what is shown in FIG. 4).In this manner, wiring to a field device may be decoupled from thecontrol system to facilitate maintenance or to remove power to the fielddevice (e.g., provided from the external power source 220 of FIG. 2).

In some examples, to communicatively couple the termination module 124 ato the universal I/O bus 210 of FIG. 2, the terminal block 300 isprovided with a plurality of baseplate connectors 310. As describedabove, in some examples, at least one of the baseplate connectors 310couples the termination module 124 a to the universal I/O bus 210 whileat least one other baseplate connector 310 couples the terminationmodule 124 a to the local power bus 216 to provide power to thetermination module 124 a and the associated field device from theexternal power source 220. That is, unlike some known terminal blockswhere all connectors to the baseplate 202 directly couple the universalI/O bus 210 with a termination module, the terminal block 300 of theillustrated example provides separate connections to each of theuniversal I/O bus 210 and the local power bus 216. The baseplateconnectors 310 may be implemented using any suitable interfaceincluding, for example, an insulation piercing connector, a knifeconnector, etc. In this manner, the termination module 124 a can enableboth communications to the I/O bus 210 and power delivery to acorresponding field device. More particularly, to enable communicatinginformation between the termination module 124 a and the I/O bus 210,the baseplate connectors 310 coupled to the I/O bus 210 are alsointernally connected to one or more of the contacts 302 of thetermination module 124 a. Likewise, to enable power transmission betweenthe termination module 124 a and the field device, the baseplateconnectors 310 coupled to the local power bus 216 are also internallyconnected to one or more different ones of the contacts 302 of thetermination module 124 a.

In some examples, the terminal block 300 is provided with a field deviceinterface such as wire termination points 306 to secure (e.g., viamoveable cage clamps actuated by screws 308) conductive communicationmedia (e.g., a bus wire) from a field device (e.g., the field device 112a of FIG. 1). More particularly, in some examples, the field device 112a is a 3-wire DI field device. In some such examples, each of the threewire termination points 306 of the terminal block 300 is to receive oneof the three wires from the 3-wire field device. When the terminationmodule 124 a is removably coupled to the terminal block 300, thetermination points 306 are communicatively coupled to one or more of thecontacts 302 of the termination module 124 a to enable communicatinginformation between the termination module 124 a and the field device112 a. Additionally, in some examples, the termination points 306 arecommunicatively coupled to one or more of the contacts 302 to enablepower transmission between the termination module 124 a and the fielddevice 112 a based on power from the external power source 220.

In other example implementations, the terminal block 300 may be providedwith any other suitable type of field device interface (e.g., a socket)instead of the termination screws 308. In addition, although one fielddevice interface (e.g., the termination points 306 with the screws 308)is shown, the terminal block 300 may be provided with more field deviceinterfaces configured to enable communicatively coupling a plurality offield devices to the termination module 124 a.

With the example termination block 300 electrically coupled to the localpower bus 216, there is the possibility that a short circuit associatedwith the corresponding termination module 124 a and corresponding fielddevice may occur and draw away power from other termination modules inother terminal blocks on the baseplate 202. Accordingly, in theillustrated example, the termination block 300 is provided with a fuse312 to protect other termination modules (in other terminal blocks) fromlosing power. In some examples, the fuse is replaceable. In this manner,the cost of acquiring and wiring a separate external fuse is eliminated.Furthermore, incorporating the fuse 312 into the terminal block 300reduces the overall footprint of the system.

FIG. 5 is a schematic illustration of an example implementation of theexample terminal block 300 of FIGS. 3 and 4 wired to a 3-wire fielddevice 502 (e.g., corresponding to the field device 112 a of FIG. 1). Insome examples, the field device 502 is a discrete input (DI) fielddevice, such as, for example, photoelectric or capacitive sensors,switches, or other such DI devices that need power to operate. In theillustrated example, the terminal block 300 is communicatively coupledto the baseplate 202 that provides power 504 from the external powersource 220. Further, in the illustrated example of FIG. 5, the terminalblock 300 is communicatively coupled to the termination module 124 athat provides isolation and control circuitry 506 to enablecommunications between the field device 502 and the controller 104(FIG. 1) as described more fully in U.S. Pat. Nos. 8,332,567; 8,762,618;9,495,313; and 9,411,769; all of which were incorporated above.

As shown in the illustrated example of FIG. 5, each of the three wiresof the field device 502 is landed directly onto one of the threetermination points 306 of the terminal block 300. Signaling andelectrical power delivery are accomplished through the internal wiringand design of the terminal block 300 (including the baseplate connectors310) in relation to the termination module 124 a and the baseplate 202(that may be coupled to the external power source 220). Furthermore, insome examples, the terminal block 300 includes the fuse 312 built intothe terminal block 300 between the termination points 306 and thebaseplate 202 (through which power is provided) to provide short circuitprotection.

For purposes of comparison, FIG. 6 illustrates a schematicimplementation of the 3-wire DI field device 502 wired to thetermination module 124 a using a known terminal block 602 constructed tohandle common 2-wire architectures. As described above, to implement a3-wire field device, there is the need for an external power source.Unlike the illustrated example of FIG. 5, the terminal block 602 of FIG.6 is not equipped to provide power through the baseplate 202. As aresult, an external power source 604 must be separately coupled to the3-wire field device 502. In such scenarios, interfacing the 3-wire fielddevice 502 with both the external power source 604 and the terminalblock 602 may require three intermediate terminals 606. Furthermore,additional wires 608 may be required to land on the terminal block 602and to electrically couple to the external power source 604 via twoadditional terminals 610. Further still, with the external power source604 wired in, there is also a need for an external fuse 612 to protectagainst short circuits. Each of the terminals 606, 610, the wires 608,and the fuse 612 shown in FIG. 6 are additional and separate componentsadding to the cost and complexity to a control system that may beavoided using the example terminal block 300 shown in FIG. 5.Furthermore, the example implementation shown in FIG. 5 has a muchsmaller footprint than what is shown in FIG. 6 because the additionalcomponents are either excluded or incorporated within the terminal block300.

Although the external power source 220 still needs to be wired to thebaseplate 202 to provide power in the illustrated example of FIG. 5, insome examples, this wiring only needs to be performed once for all fielddevices communicatively coupled to the baseplate 202. In some examples,the baseplate 202 holds up to twelve terminal blocks and correspondingtermination modules. By contrast, using known techniques, as shown inFIG. 6, each additional 3-wire field device would need to be separatelycoupled to the external power source 604, thereby further increasing thecost and complexity of setting up and maintaining the control system.

FIG. 7 is a schematic illustration of an example implementation of theexample terminal block 300 of FIGS. 3 and 4 wired to a 2-wire fielddevice 702 (e.g., which may be similar or identical to the field device112 a of FIG. 1). While the terminal block 300 may be advantageouslyemployed to communicatively couple a 3-wire field device as shown inFIG. 5, in some examples, the terminal block 300 may also be used tocommunicatively couple with a common 2-wire field device as illustratedin FIG. 7. In some examples, the 2-wire field device 702 is powered viathe external power source 220. As a result, the example terminal block300 disclosed herein may be used to communicatively coupled either a2-wire field device or a 3-wire field device to a process controlsystem.

Although certain example apparatus have been disclosed herein, the scopeof coverage of this patent is not limited thereto. On the contrary, thispatent covers all methods, apparatus and articles of manufacture fairlyfalling within the scope of the claims of this patent.

What is claimed is:
 1. A terminal block, comprising: a first interfaceincluding termination points to couple with a field device; a secondinterface to be removably coupled with a shared bus of a terminationpanel, wherein the terminal block is to be removably coupled to theshared bus; a third interface to couple with a power bus of thetermination panel; and a fuse disposed between the first interface andthe third interface.
 2. The terminal block of claim 1, wherein thesecond interface removably receives a first termination module tocommunicate with the field device via the first interface using a firstcommunication protocol.
 3. The terminal block of claim 2, wherein thefirst termination module communicates with a controller via the sharedbus using a second communication protocol different than the firstcommunication protocol.
 4. The terminal block of claim 2, wherein thesecond interface removably receives a second termination module in placeof the first termination module to communicate with a second fielddevice via the first interface using a second communication protocoldifferent than the first communication protocol.
 5. The terminal blockof claim 2, wherein the first termination module is replaceable with asecond termination module while the first interface is communicativelycoupled to the field device.
 6. The terminal block of claim 2, whereinthe first termination module is replaceable with a second terminationmodule while the second interface is communicatively coupled to theshared bus.
 7. The terminal block of claim 2, further including amoveable latch that releases the first termination module, secures thefirst termination module in an installed position, or secures the firsttermination module in a partially installed position.
 8. The terminalblock of claim 7, wherein the partially installed position correspondsto the first termination module being held in place within a slot of theterminal block while preventing electrical contact between contacts ofthe first termination module and the second interface.
 9. The terminalblock of claim 1, wherein the power bus provides power to the fielddevice from an external power source, the power bus separate from theshared bus.
 10. The terminal block of claim 1, wherein the field deviceis at least one of a two-wire field device, a two-wire discrete inputfield device, a three-wire field device, or a three-wire discrete inputfield device.
 11. The terminal block of claim 1, wherein the fuse isremovably coupled to the third interface.
 12. A termination panel,comprising: a shared bus; a power bus; a plurality of terminal blocks tocouple with a controller via the shared bus, at least a first one of theterminal blocks including: a first interface including terminationpoints to couple with a field device; a second interface to be removablycoupled with the shared bus, wherein the first one of the terminalblocks is to be removably coupled to the shared bus; a third interfaceto couple with the power bus; and a fuse disposed between the firstinterface and the third interface.
 13. The termination panel of claim12, wherein the first terminal block is coupled to an I/O card includedin the controller via the shared bus.
 14. The termination panel of claim12, wherein the I/O card is a first I/O card and the shared bus is afirst shared bus, further including a second one of the terminal blockscoupled to a second I/O card included in the controller via a secondshared bus different than the first shared bus.
 15. The terminationpanel of claim 12, wherein the power bus provides power to the fielddevice from an external power source, the power bus separate from theshared bus.
 16. The termination panel of claim 12, wherein the fuse isremovably coupled to the third interface.
 17. The termination panel ofclaim 12, further including disposing the termination panel in amarshalling cabinet.
 18. A process control system, comprising: acontroller; a termination panel including a shared bus and a power bus,the termination panel including: a plurality of terminal blocks coupledto the termination panel to couple with the controller via the sharedbus, at least a first one of the terminal blocks including: a firstinterface including termination points to couple with a field device; asecond interface to be removably coupled with the shared bus, whereinthe first one of the terminal blocks is to be removably coupled to theshared bus; a third interface to couple with the power bus; and a fusedisposed between the first interface and the third interface.
 19. Theprocess control system of claim 18, wherein the second interfaceremovably receives a first termination module to communicate with thefield device via the first interface using a first communicationprotocol.
 20. The process control system of claim 19, wherein thecontroller is communicatively coupled to the first termination modulevia the second interface using a second communication protocol differentthan the first communication protocol, and further including aworkstation communicatively coupled to the controller using a thirdcommunication protocol different than the first and second communicationprotocols.